There are cases where a processor needs to be defined but not start/stop by the StreamService.
For instance, an import processor can be registered and start/stop using a REST API.
Another case is when having different processors that work together, we may want to initialized all the streams first and then control the order the processors are started.
We can add start flag:
Also, some a processor can use source or sink streams defined by other processor and in this case, we don't want to create conflict during initialization (streams being defined by both processor).
We can add an external flag to the stream configuration: